>>8644988
we don't really know, they seem proper at first, you could argue they are secret masochists that really got off on the thrill of fucking their best friend's son and neighbor, and it escalated so much they're literally just down to fuck whichever now even their own son. It's a nice case of them becoming more slutty each time they get fucked, peaking on incest and their impregnation. It's also great and heavily hinted that they will simply just keep fucking whatever kids they get and make incest a family tradition.